NMR characterization of structural and dynamics perturbations due to a single point mutation in Drosophila DLC8 dimer: functional implications.

Dynein light chain protein (DLC8), the smallest subunit of the dynein motor complex, acts as a cargo adaptor. The protein exists as a dimer under physiological conditions, and cargo binding occurs at the dimer interface. Dimer stability and relay of perturbations through the dimer interface can thus be anticipated to play crucial roles in the variety of functions the protein performs. Recent investigations point out that DLC8 also gets phosphorylated at Ser 88, which is located at the extreme C-terminal end. In this background, we investigate here by NMR the effects of a small perturbation by way of a single point mutation, S88A, on the structure, dynamics, and cargo binding efficacy of the DLC8 dimer. We observe that the perturbation travels far away along the sequence from the site of the mutation. This relay has been explained at the atomic level by looking into the packing of the side chains in the crystal structure of the protein. It follows that the interface is highly adaptable, which may account for the versatility of the dimer's cargo binding ability. Binding studies with a peptide indicate that the mutation compromises binding efficacy. These observations show how remote residues that may not be directly bound to a target can still affect the affinity of the protein to the target. Furthermore, the S88A mutational perturbations seen here in Drosophila DLC8 are dramatically different from those of the same mutation in human DLC8 (also known as DLC1) ( Song, C. , et al., ( 2008) J. Biol. Chem, 283, 4004- 4013. ) which differs from Drosophila DLC8 at only five locations. All of these observations put together highlight the sensitivity of dynein light chain protein to small perturbations, and this would have great functional implications.